RCS reduction of a cylindrical cavity by dielectric coating

Lee, C.; Lee, S.; Chou, Ri-Chee

doi:10.1109/aps.1986.1149727

Cited by 10 publications

(5 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The local equilibrium is always maintained according to their calculation. Turnbull et al [36] simulated the desorption rate of Lee and Lee [28,42] by choosing 0t ϭ 2.2 ϫ 10 7 s Ϫ1 (calculated by the present authors using the relation ϭ N L k, N L ϭ 5.1 ϫ 10 29 sites/m 3 ) and 0d ϭ 2.1 ϫ 10 7 s Ϫ1 . They deduced the activation energy from the slope of the simulated ln (/T p 2 ) Ϫ 1/T p plot as adopted by Lee and Lee.…”

Section: Discussionmentioning

confidence: 98%

Precise determination of the activation energy for desorption of hydrogen in two Ti-added steels by a single thermal-desorption spectrum

Wei

Hara

Tsuzaki

2004

Metall Mater Trans B

159

View full text Add to dashboard Cite

Critical assessment of the existing models for the desorption rate of hydrogen trapped in steel indicated that the desorption rate can be described by the kinetic formula dX/dt ϭ A(1 Ϫ X) exp (ϪE d /RT). Good fit of the formula has been found to the hydrogen released during thermal-desorption spectrometry (TDS) analysis from the coherent and incoherent TiC particles in 0.05C-0.22Ti-2.0Ni and 0.42C-0.30Ti steels. The activation energy (E d ) and the constant parameter A can be determined uniquely with high accuracy by a single spectrum simulation. The activation energy for hydrogen desorption from the incoherent TiC particle in the well-tempered 0.05C-0.22Ti-2.0Ni steel is 85.7 kJ/mol. In the 0.42C-0.30Ti steel, a higher activation energy of 116 kJ/mol was obtained for the coarse incoherent TiC when tempered at 650 °C and 700 °C. The activation energy decreased from 116 kJ/mol at 650 °C to 68 kJ/mol at 500°C. The nanosized TiC coherent precipitates in the 0.42C-0.30Ti steel were found to have an activation energy ranging from 46 to 59 kJ/mol, depending on the tempering temperature. A low value of much less than 10 4 s Ϫ1 was obtained for the constant parameter A for most cases, which suggested that the retrapping of the released hydrogen is not important in the thermal-desorption analysis.

show abstract

Section: Discussionmentioning

confidence: 98%

Precise determination of the activation energy for desorption of hydrogen in two Ti-added steels by a single thermal-desorption spectrum

Wei

Hara

Tsuzaki

2004

Metall Mater Trans B

159

View full text Add to dashboard Cite

show abstract

“…An advanced fighter aircraft should have not only excellent aerodynamic performance but also sufficient electromagnetic performance to cope with the increasingly complex electromagnetic detection environment. Due to the cavity configuration, the intake significantly influences the forward electromagnetic scattering characteristics of an aircraft [1]. Therefore, reducing the intensity of radar echo while ensuring the aerodynamic performance of the intake is particularly important when designing advanced fighter aircraft.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of Aerodynamic and Electromagnetic Performances for S-Duct Caret Intake with Boundary-Layer Bleed System

Wang

2023

International Journal of Aerospace Engineering

View full text Add to dashboard Cite

This study presents the numerical results for the aerodynamic and electromagnetic performances of an S-duct caret intake. Using the multilevel fast multipole method (MLFMM) to solve Maxwell equations, the current on the intake surface is calculated, and the radar cross-section (RCS) is analyzed. Moreover, the intake flow field is numerically investigated using the SST k–ω turbulence model to solve the Reynolds-averaged Navier–Stokes equations. Compared to a straight intake, for an S-duct caret intake, the average RCS is lower by 7.65 dB, and the maximum RCS difference value caused by the blade rotation is lower by 6.75 dB. However, the flow capacity deteriorates when the total pressure recovery coefficient decreases by 0.004. Based on the analysis of the aerodynamic and electromagnetic characteristics of different intakes, a double S-duct intake is designed. Compared to a traditional S-duct intake, for the novel intake after model parameter modification, the average RCS is lower by 0.05 dB, and the total pressure distortion (TPD) is lower by 0.18. The analysis of the effects of different boundary-layer bleed systems shows that the symmetrical layout adversely affects the aerodynamic and electromagnetic performances of the S-duct intake, but the unilateral partial layout is beneficial, whose TPD is lower by 0.04 and average RCS is higher by −2.17 dB compared to a straight intake.

show abstract

“…Recently, various unmanned aerial vehicles have been designed all over world with the rapid development of related technology. Considering that the intake is one of the main electromagnetic scattering centers of aircrafts [1], the design of intakes has become a technical difficulty in UAV research. The S-duct intake is usually designed such as a short-distance diffuser, which is prone to secondary flow separation and flow distortion, resulting in the loss of aerodynamic performance.…”

Section: Introductionmentioning

confidence: 99%

Numerical Optimization of Electromagnetic Performance and Aerodynamic Performance for Subsonic S-Duct Intake

Wang

2022

Aerospace

View full text Add to dashboard Cite

In order to improve the performance of subsonic unmanned aerial vehicle (UAV), a knapsack S-duct intake has been designed. The influences of an S-bend diffuser on aerodynamic performance and electromagnetic performance were analyzed firstly. The viscous flow field has been simulated by solving Favre averaged Navier–Stokes equations using a shear stress transport (SST) k-ω turbulence model. The surface current has been simulated by solving Maxwell equations using a multi-level fast multipole method (MLFMM). The multi-objective optimization of the S-duct intake was studied by using the diffuser as the optimized object. The parametric expression of the diffuser model was realized using the fourth order function geometric representation technique. The efficient model based on the Kriging model and non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ) were used to accelerate the optimization progress. By analyzing the results of an optimal intake chosen from the Pareto front, the total pressure distortion (TPD) index DC60 has decreased by 0.24 at the designed Mach number of 0.9, and the average Radar Cross Section (RCS) has decreased by 2db at the frequency of 3GHz. The optimized S-duct intake could have both excellent aerodynamic performance and electromagnetic performance at various complex conditions.

show abstract

RCS reduction of a cylindrical cavity by dielectric coating

Cited by 10 publications

References 2 publications

Precise determination of the activation energy for desorption of hydrogen in two Ti-added steels by a single thermal-desorption spectrum

Precise determination of the activation energy for desorption of hydrogen in two Ti-added steels by a single thermal-desorption spectrum

Numerical Investigation of Aerodynamic and Electromagnetic Performances for S-Duct Caret Intake with Boundary-Layer Bleed System

Numerical Optimization of Electromagnetic Performance and Aerodynamic Performance for Subsonic S-Duct Intake

Contact Info

Product

Resources

About